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1.5 Exponentials and logarithms

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Question 7
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The temperature, θ∘C\theta^\circ\text{C}θ∘C, of a cup of tea t t\,t minutes after measurements began, is modelled using the formula θ=68e−0.15t+21,t≥0\theta = 68e^{-0.15t} + 21, t \geq 0θ=68e−0.15t+21,t≥0

a.

Sketch the graph of θ \theta\,θ against ttt.

[2]
b.

Find according to the model the initial temperature of the tea.

[1]
c.

Find the value of t t\,t when the cup of tea reaches 40∘C40^\circ\text{C}40∘C.

[3]
Markscheme

1.5 Exponentials and logarithms Questions

  1. A Level
  2. /Maths
  3. /1.5 Exponentials and logarithms

77 exam-style questions on CCEA A Level Maths 1.5 Exponentials and logarithms, covering 1.5.1 Exponentials and logarithms, 1.5.2 Exponentials and logarithms, 1.5.3 Exponentials and logarithms, 1.5.4 Exponentials and logarithms, 1.5.5 Exponentials and logarithms, 1.5.6 Exponentials and logarithms, 1.5.7 Exponentials and logarithms, and 1.5.8 Exponentials and logarithms. Each one has a worked solution and a mark scheme showing where the marks go.

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